Single AC fleets mean an airline has somewhat of a single point of failure. If the issue at hand is caused by that point of failure, sure recovery will be harder. In most other cases it makes it actually easier, at least on paper. No need to get crews to certain planes, just a crew to a plane, as every crew is certified on any plane.

And people wonder why Boeing made such an effort to not need different pilot training for the MAX.

People don't really wonder that though. The potential for it to be beneficial to their customers is obvious.

I wondered always why people wondered. Airbus went to great length to make cross-certification of pilots possible for that very reason.

Nobody is wondering anything. Advantages are obvious. They were wondering why you’d prioritize that over the aircraft’s ability to stay in the air.

I've followed many 737MAX threads on HN, and they sure did dismiss this issue. It was always "why didn't they design a whole new airplane from the ground up".

> why you’d prioritize that over the aircraft’s ability to stay in the air.

This is an egregious misunderstanding. There was nothing wrong with the purpose of the the MCAS system nor the concept of it. What went wrong was its failure to follow the dual path design, and do a proper failure analysis of its design. There was a further problem with some pilots not understanding how to deal with stab trim runaway.

These problems have since been corrected, and MCAS is still on the 737MAX.

To be fair, there is more than one way to skin a cat, though it wouldn’t have worked for Southwest.

They could’ve made a small sized aircraft that had commonality with the 787 rather than the 737.

IIRC a few 737MAXs fell out of the sky. Clearly there being nothing wrong with the purpose nor concept of MCAS wasn't sufficient to keep the airplane from crashing.

MCAS in itself doesn't seem to have been the problem. The fact that MCAS relied on a single sensor (no idea how that got certified in the first place) and that pilot were not aware of MCAS and how it worked were the problems. The latter was due to Boeing trying to avoid re-training and re-certification of air crew.

> pilot were not aware of MCAS and how it worked were the problems

If the pilots followed runaway trim procedure, which is how the MCAS failure manifested, they would have been fine. In fact, that's what the other unmentioned crew of a 737MAX did that survived MCAS malfunction and landed without incident.

Boeing issued an Emergency Airworthiness Directive about the procedure, which the Egyptian Air pilots didn't follow, either.

I thought there were some conditions in which manually adjusting trim became physically impossible (or at least extremely difficult).

If the wheels fall off your car, is the problem with the purpose or concept of wheels, or is the problem with weak axles?

Errr... I never said anything at all was wrong with MCAS.

The utilization rate is so high that specific planes and crew are needed in specific times and places.

If plane going from A -> B is late it cannot become flight B -> C. If crew for this plane are stuck in the ground long enough, they have to wait til the next day to fly as they‘re only allowed to be awake and work for so long.